1. Field of the Invention
This invention relates generally to contraception, and specifically to a biological contraceptive for males.
In the case of humans, overpopulation remains one of the most critical problems facing humankind. In recent times, the contraceptive pill has been successfully employed by women to prevent ovulation and conception. However, the contraceptive pill designed for use by women consists of steroids (a mixture of progestagens and estrogens) and there is considerable concern about its potentially harmful sideeffects following prolonged use. There is thus at present considerable pressure to block the reproductive capacity in the male and to not place all the chemical and psychological burden on the female.
Methods of male fertility control are also highly desireable in the case of animals, especially as simpler alternatives to the present procedures of castration or other forms of surgical sterilization.
An ideal chemical contraceptive for the male would be one which effectively arrests spermatogenesis (i.e. stops formation of sperm cells) or blocks the fertilizing capacity of sperm, without affecting testicular steroidogenesis (production of male steroid hormones), libido, accessory sex glands, and pituitary function, in the absence of toxic or other undesireable side effects. The procedure would be simple, non-surgical, and preferably expose only the sperm producing tissue to the compound, thus avoiding distribution of foreign chemicals to non-reproductive tissues in the body. Infrequent application of the treatment would also be desirable.
2. Description of the Prior Art
An "ideal" male contraceptive agent has not been described in the prior art, although many compounds have been explored for the purpose of inhibiting or arresting spermatogenesis (see Bennett, J. P. (1974), Chemical Contraception, Columbia Press, New York, pp. 133-170; Davies, A. G. (1980), Effects of Hormones, Drugs and Chemicals on Testicular Function, Vol. 1, Eden Press, Westmont, pp. 123-164; and Jeffcoate, S. L. and Sandler, M. (Editors), Progress Towards a Male Contraceptive, John Wiley and Sons, Chichester, 1982). While many of the compounds tested in the past possess some anti-spermatogenic or anti-fertilizing capacity, their contraceptive action is invariably overshadowed by their cytotoxic, neurotoxic or anti-metabolic effects, or by their untoward effects on libido, accessory sex glands and the male endocrine system (see Jeffcoate and Sandler, supra). Moreover, the compounds that have been tested generally require fairly large daily doses and their long range effects remain unknown (see Shandilya, L., Clarkson, T. B, Adams, M. R., and Lewis, J. C. (1982). "Effects of gossypol on reproductive and endocrine functions of male cynomolgus monkeys (Macaca fascicularis)", Biol. Reprod. 27:241-252).
Vasectomy is of course a proven technique, but it requires surgery, albeit relatively minor surgery. Epididymal sperm congestion and sperm cysts and sometimes autoimmune reactions are observed.
Although castration will effectively remove sperm production, it also removes the source of male sex steroid hormones and as such is unacceptable for human males. Castration is often employed on pets and farm animals, but it requires aseptic surgery and a period of healing and thus is relatively complicated.